This avoids explicitly including gl or egl headers in
clutter-egl-headers.h. We were getting build failures when building
clutter against a libcogl that has runtime support for GL and GLES
because cogl-defines.h was including gl.h and then clutter-egl-headers.h
was later including GLES2/gl.h with typedef conflicts. Clutter relies on
Cogl to abstract GL and GLES and the winsys APIs like EGL and GLX so
Clutter should just rely on cogl.h to include the appropriate egl.h in
clutter-egl-headers.h.
Reviewed-by: Emmanuele Bassi <ebassi@linux.intel.com>
Reviewed-by: Neil Roberts <neil@linux.intel.com>